It is known that adenosine antagonistic action is found in compounds represented by Formula (A) in which R.sup.1a and R.sup.2a represent propyl, R.sup.3a represents hydrogen, and R.sup.4a represents substituted or unsubstituted phenyl, aromatic heterocyclic group, cycloalkyl, styryl, or phenylethyl [J. Med. Chem., 34, 1431 (1991)]. Further, Japanese Published Unexamined Patent Application No. 26516/72, as cerebral stimulants, compounds represented by Formula (B) in which R.sup.1b and R.sup.2b independently represent methyl or ethyl, R.sup.3b represents methyl, Y.sup.1b and Y.sup.2b represent hydrogen, and Z.sup.b represents phenyl or 3,4,5-trimethoxyphenyl WO92/06976 discloses, as compounds having an adenosine A.sub.2 receptor antagonistic activity and therapeutic effects on asthma and osteoporosis, compounds represented by Formula (B) in which R.sup.1b and R.sup.2b independently represent hydrogen, propyl, butyl, or allyl, R.sup.3b represents hydrogen or lower alkyl, Y.sup.1b and Y.sup.2b independently represent hydrogen or methyl, and Z.sup.b represents phenyl, pyridyl, imidazolyl, furyl, or thienyl unsubstituted or substituted by 1 to 3 substituents such as lower alkyl, hydroxy, lower alkoxy, halogen, amino, and nitro. Furthermore, other compounds represented by Formula (B) are known. One is 8-styryl caffeine which is a compound of Formula (B) in which R.sup.1b, R.sup.2b, and R.sup.3b represent methyl, Y.sup.1b and Y2b represent hydrogen, and Z.sup.b represents phenyl [Chem. Ber., 119, 1525 (1986)]. Another is a compound of Formula (B) in which R.sup.1b, R.sup.2b, and R.sup.3b represent methyl, Y.sup.1b and Y.sup.2b represent hydrogen, and Z.sup.b represents pyridyl, quinolyl, or methoxy-substituted or unsubstituted benzothiazolyl [Chem. Abst., 60, 1741h (1964)]. However, there is no description with regard to the pharmacologic action of any of these compounds.
It is clinically well known that the conventional antidepressant exhibits little effect in a single administration, and the effect is observed after at least about two weeks' consecutive administration. With the conventional antidepressant, the enhancement of clonidine-induced aggressive behavior in mice is observed after at least ten days' consecutive administration [J. Neural Transmission, 52, 189 (1981)].